Copolymers of tetrafluoroethylene (TFE) and a co-monomer according to the formula: FSO2—CF2—CF2—O—CF(CF3)—CF2—O—CF═CF2 are known and sold in sulfonic acid form, i.e., with the FSO2— end group hydrolyzed to HSO3—, under the trade name Nafion® by DuPont Chemical Company, Wilmington, Del. Nafion® is commonly used in making polymer electrolyte membranes for use in fuel cells.
Copolymers of tetrafluoroethylene (TFE) and a co-monomer according to the formula: FSO2—CF2—CF2—O—CF═CF2 are known and used in sulfonic acid form, i.e., with the FSO2— end group hydrolyzed to HSO3—, in making polymer electrolyte membranes for use in fuel cells.
U.S. patent application Ser. No. 10/325,278, filed Dec. 19, 2002, the disclosure of which is incorporated herein by reference, discloses a polymer electrolyte membrane having a thickness of 90 microns or less and comprising a polymer, said polymer comprising a highly fluorinated backbone and recurring pendant groups according to the formula:YOSO2—CF2—CF2—CF2—CF2—O—[polymer backbone]where Y is H+ or a monovalent cation such as an alkali metal cation. Typically, the membrane is a cast membrane. Typically, the polymer has a hydration product of greater than 22,000. Typically, the polymer has an equivalent weight of 800-1200.
International Patent Application Publication No. WO 01/27167 purportedly discloses a crosslinked fluorocarbon polymeric composition having hydrophilic functional groups which is crosslinked with fluorinated crosslinking groups.
U.S. Patent Application Publication No. 2003/0032739 discloses a covalently crosslinked polymer or polymer membrane consisting of one or more polymers, which may bear precursors of cation exchange groups, which are crosslinked through the reaction of sulfinate groups —SO2Me on the polymer with crosslinkers which may include halo aromatics to form cross-linking bridges which may include: polymer-SO2-arylene-SO2-polymer.
U.S. Pat. No. 6,090,895 discloses a method for making crosslinked acidic polymers useful as ion conductive membranes, such as crosslinked sulfonated polyether ketones, sulfonated polysulfones, sulfonated polystyrenes, and other acidic polymers, by crosslinking with a species which generates an acidic functionality. The crosslinker preferably binds to acid functions by conversion of acid groups to imide functionality, which, due to the acidity of the N—H bonds therein, compensate for the acidity lost by the occupation of the acid groups and thus preserve membrane conductivity while contributing to membrane strength and resistance to swelling.
U.S. Patent Application Publication No. 2003/0092940 discloses a method for making aromatic-imide and aromatic-methylidynetrissulfonyl species by reaction of aromatic species with a reactant according to the formula:(X—SO2—)m-QH—(—SO2—R1)n wherein Q is C or N; wherein each X is independently selected from the group consisting of halogens, typically F or Cl; wherein each R1 is independently selected from the group consisting of aliphatic and aromatic groups, which may or may not be straight-chain, branched, cyclic, heteroatomic, polymeric, halogenated, fluorinated or substituted; wherein m is greater than 0; wherein m+n=2 when Q is N; and wherein m+n=3 when Q is C. Ar may be derived from an aromatic polymeric compound. In addition, the reference discloses compounds according to the formula: (Ar—SO2—)m-QH—(—SO2—R1)n wherein R1 comprises a highly acidic group selected from sulfonic acid, carboxylic acid and phosphonic acid, and Ar is derived from an aromatic compound.